While coal tar and petroleum pitches commonly used for electrode manufacturing have approximately the same softening points, the coat tar pitch is usually higher in Conradson carbon than petroleum pitch having the same softening point. The higher the Conradson carbon, the higher the product yield. The two pitches also have different quinoline insoluble portions with the coat tar pitch having, generally, a higher quinoline insoluble content than the petroleum pitch. In addition, the form of the quinoline insolubles in petroleum pitch is a different form than that in the coal tar pitch the latter being non-optically active.
Efforts to prepare petroleum pitch which would meet the specifications of coal tar pitch have been generally unsuccessful since the polymerization of the residual oil from which petroleum pitch is normally derived produces a pitch which has a quinoline insolubles (QI), of no more than 4 to 4.5, at which point there is phase separation and coking at the reactor walls. Thus petroleum pitch could not meet many coal tar pitch specifications which require that the QI's be in the range of 10 to 15%.
Thus it would be advantageous to provide a process which could employ petroleum pitch and meet the requirement specifications of coal tar pitch.